The present invention relates to a control method for controlling an excavator. Besides, the present invention relates to an excavator comprising a control unit implementing such a control method.
The invention can be applied in construction equipment machines, such as mechanical shovels or drillers and any other type of excavator. Such excavator may be a tracked swilling excavator comprising either a caterpillar track or wheels, and a cantilever member coupled to a rotating platform mounted on the caterpillar track.
The invention can also be applied to wheeled excavators and or to backhoe loaders. Although the invention will be described with respect to a mechanical shovel, the invention is not restricted to this particular construction equipment, but may also be used in other construction equipment machines.
W013114451A1 discloses an excavator including several movable members and several electric actuators to actuate said movable members, several static brakes to lock said electric actuators, a command device to receive commands from an operator and a control unit to control said electric actuators and said static brakes.
Each electric actuator usually comprises a rotational electric motor which can rotate in either way (reversible). The static brakes maintain the electric actuator in an idle, static position over long periods, so that the electric actuators can hold the loads or torques without consuming electric power. A static brake can for instance be formed by a gear lock.
When the operator handles the command device in order to command a motion of a movable member, the control unit releases a first static brake so as to move the corresponding electric actuator. Then, the control unit often needs to release a second static brake so as to move another electric actuator, in particular when the required motion commands a large motion amplitude. The control unit can successively release several static brakes until the required motion is complete.
However, when the second static brake is released while the first one is moving, there is a risk of backlash or small bump, which decreases the operator's comfort and may reduce the service life of some components of the excavator.
It therefore appears that, from several standpoints, there is room for improvement in the control methods for controlling an excavator and in the excavator including a control unit implementing such a control method.
It is desirable to provide a control method which reduces or avoids the risk of backlash when several electric actuators have to work simultaneously or concomitantly.
According to one aspect of the invention, a control method, for controlling an excavator, includes a step of:
providing an excavator including at least:
several movable members, each movable member being configured to move at least a part of said excavator,
at least one actuating set comprising at least two actuators, said at least two actuators including at least one electric actuator, each actuator being configured to actuate at least one of said movable members,
at least one static brake movable between a locking position where said at least one static brake locks said at least one electric actuator and an unlocking position where said at least one static brake unlocks said at least one electric actuator,
a command device configured to receive commands from an operator and to generate command signals based on said commands,
a control unit configured to receive said command signals and to control said actuators and said at least one static brake based on said command signals.
Furthermore, this control method includes at least:
a reception step wherein said control unit receives a command signal,
an actuation check step wherein said control unit checks whether said command signal requires said control unit to actuate at least one actuator belonging to said at least one actuating set, and
in case said command signal requires said control unit to actuate an actuator belonging to said at least one actuating set, an unlocking step wherein said control unit controls said at least one static brake so that said at least one static brake moves towards its unlocking position.
Thus, such a control method allows the excavator to generate smooth motions with small or null backlash in case two or more movable members need be moved concomitantly. By the provision of such an excavator arm, one advantage of such a control method is the reduction of the risk of backlash when several electric actuators have to work simultaneously or concomitantly, as compared to the excavator of W013114451A1. Indeed, during the unlocking step, the control unit causes the unlocking of the or each electric actuator belonging to the or each actuating set.
According to a variant, said at least one actuating set may comprise at least one hydraulic actuator. For instance, said at least one actuating set may comprise one hydraulic actuator and one electric actuator. Thus, when the operator sends a command which requires the control unit to first operate the hydraulic actuator, the control unit unlocks the static brake from locking the electric actuator during the unlocking step. Releasing the or each electric actuator allows a smooth motion (hence with little or no backlash) when the movable member gets afterwards actuated by the operator of the excavator.
According to an embodiment, said control unit can control said at least one static brake so that said at least one static brake moves towards its unlocking position within less than 500 milliseconds, preferably within less than 100 milliseconds.
Thus, unlocking the or each static brake is so quick that the operator of the excavator can hardly, if ever, feel any backlash.
According to an embodiment, said at least one actuating set may comprise at least two electric actuators; said excavator includes at least two static brakes, each static brake being movable between: i) a respective locking position where said static brake locks a respective electric actuator, and ii) a respective unlocking position where said static brake unlocks said respective electric actuator; and, during said unlocking step, said control unit controls each static brake so that each static brake moves towards its respective unlocking position.
Thus, such an actuating set provides for smooth motions upon successive actuating of the electric actuators belonging to the actuating set.
According to a variant of the previous embodiment, said at least one actuating set may comprise only electric actuators. In other words, said at least one actuating set does not comprise any other kind of actuator, in particular no hydraulic actuator, apart from electric actuators. During the unlocking step, the control unit controls each static brake so that each static brake moves towards its respective unlocking position. Such an all-electric actuating set makes it possible to get rid of all the components required for hydraulic actuators, like fluid hoses, pumps and the like.
According to an embodiment, said actuators belonging to said at least one actuating set can be configured to cooperate in order to generate a combined motion of at least one of said movable members.
Thus, such a control method allows the excavator to generate smooth combined motions with small or null backlash when two adjacent movable members are moved either successively or concomitantly.
According to an embodiment, the control method further includes an actuation step wherein said control unit actuates at least two actuators belonging to said at least one actuating set when said command signal requires said control unit to actuate said at least two actuators belonging to said at least one actuating set.
Thus, such actuation step allows the excavator to generate smooth motions with small or null backlash when two movable members are moved concomitantly.
According to an embodiment, said at least one electric actuator can be selected in the group consisting of a linear electric actuator and a rotational electric actuator.
According to a variant, said at least one electric actuator can comprise a reversible mechanical linear actuator. For instance each of said electric linear actuators can comprise a ball screw, a roller screw or a buttress thread screw, the screw imparting translation to a linear actuator rod by a nut. Alternatively, said arm linear actuator can comprise an irreversible mechanical linear actuator.
According to a variant, said at least one electric actuator can comprise an electric motor, an actuating device and a gearbox configured to transmit power from said electric motor to said actuating device.
According to an embodiment, said at least one electric actuator can include a respective electric motor, and wherein, during said unlocking step, said control unit energizes said electric motor.
Thus, the electric motor can remain idle until unlocking step begins, which permits to reduce electric power consumption. Once their electric motors get energized, the electric actuators can hold the load in lieu of the static brakes.
According to an embodiment, during said unlocking step, said control unit can energize said electric motor before said at least one static brake moves towards its respective unlocking position.
Thus, such an unlocking step allows the excavator to generate smooth motions with a small or null backlash.
According to an embodiment, during said unlocking step, said control unit can energize said electric motor substantially during a period where said at least one static brake moves towards its respective unlocking position.
Thus, the excavator can be operated swiftly, because the electric actuators are already fully energized as soon as each static brake has finished unlocking each electric actuator.
According to an embodiment, during said unlocking step, said control unit can energize said electric motor of said at least one electric actuator progressively as said at least one static brake moves towards its respective unlocking position.
Thus, such a progressive energizing of each electric motor allows the excavator to generate smooth motions with a small or null backlash.
According to an embodiment, during said unlocking step, said control unit can energize said at least one electric motor so as to actuate said at least one electric actuator belonging to said at least one actuating set.
Thus, the or each electric actuator actuated moves its respective movable member.
According to an embodiment, during said unlocking step, said control unit can energize at least one electric motor so as to maintain in a static position said at least one electric actuator.
Thus, the or each electric actuator maintained static holds immobile its respective movable member.
According to an embodiment, during said unlocking step, said control unit energizes both:
at least one electric motor so as to actuate at least one of said electric actuators belonging to said at least one actuating set, and
the remaining electric motors of all of said electric actuators belonging to said at least one actuating set in order to maintain in a static position said electric actuators.
According to an embodiment, during said unlocking step, said control unit can energize all the electric motors so as to actuate all of said electric actuators belonging to said at least one actuating set.
According to an embodiment, said control unit can comprise a memory for storing at least a dataset containing data identifying each actuator belonging to said at least one actuating set.
Thus, such a memory permits to define the actuating sets prior to using the excavator, for instance depending upon the combined motions which will most likely be commanded by the operator.
According to an embodiment, said excavator can further comprise a cab, and each one of said movable members can be selected from the group consisting of a tool configured to work on a site, an arm configured to move said tool, a boom configured to move said arm, an offset member configured to offset said boom, a drive member configured to displace said cab with respect to a site ground and a blade configured to partially lift said cab.
Thus, such movable members permit to define an excavator having an extended reach and several possible motions.
According to an embodiment, said movable members can include a tool configured to work on a site and an arm configured to move said tool,
wherein said at least one actuating set can comprise a tool actuating set, said tool actuating set including at least a tool actuator configured to drive said tool and an arm actuator configured to drive said arm, and
wherein said at least one static brake can include at least a tool static brake configured to lock said tool actuator and an arm static brake configured to lock said arm actuator.
Thus, such a tool actuating set allows the excavator to generate smooth combined motions with small or null backlash when the tool and the arm are moved concomitantly.
The tool can be any kind of tool usually implemented on mechanical construction equipment. For instance, the tool can be selected from the group consisting of a bucket, a drilling tool, a hammer and a gripping tool.
Such tools can be linked to the arm via an appropriate link configured to provide a quick coupling, be it hydraulic, electric and/or mechanic, between the arm and the tool. Usually, the tool is mounted at the tip of the arm.
According to an embodiment, said movable members can further include a boom configured to move said arm,
wherein said tool actuating set can further include a boom actuator configured to drive said boom, and
wherein said static brakes can further include a boom static brake configured to lock said boom actuator.
Thus, such a tool actuating set allows the excavator to generate smooth combined motions with small or null backlash when the tool, the arm and the boom are moved concomitantly.
According to an embodiment, said movable members can further include an offset member configured to offset said boom, and wherein said tool actuating set can further include an offset actuator configured to drive said offset member, and wherein said static brakes can further include an offset static brake configured to lock said offset actuator.
According to an embodiment, said excavator can further comprise a cab, and said movable members can include a blade configured to partially lift said cab, and a drive member configured to displace said cab,
wherein said at least one actuating set can comprise a cab actuating set, said cab actuating set including at least a blade actuator configured to drive said blade, and a drive actuator configured to drive said drive member, and
wherein said at least one static brake can include at least a blade static brake configured to lock said blade actuator, and a drive static brake configured to lock said drive member.
Thus, such a cab actuating set allows the excavator to generate smooth combined motions with small or null backlash when the blade and the drive member are moved concomitantly.
According to an embodiment, said drive member can comprise at least two drive devices including a right track drive device configured to impart a translation to a right part of said excavator and a left track drive device configured to impart a translation to a left part of said excavator, and wherein said cab actuating set can be configured to actuate both said right track drive device and said left track drive device.
According to an embodiment, said movable members can further include a swing member configured to swing said cab, wherein said cab actuating set can further include at least a swing actuator configured to drive said swing member, and wherein said static brakes can include at least a swing static brake configured to lock said swing actuator.
According to a variant, said excavator can include at least two actuating sets. One or more actuator can be shared by said at least two actuating sets. Alternatively, each actuator can be dedicated to only one actuating set.
According to a variant, said excavator can include both a tool actuating set and a cab actuating set.
According to a variant, said cab actuating set can further comprise: said drive member, possibly including said right track drive device and said left track drive device,                said swing actuator, and/or        
a blade actuator configured to actuate a blade for immobilizing said excavator with respect to the site ground.
According to a variant, said at least one actuating set can include a large actuating set configured to drive numerous electric actuators. Such a large actuating set would thus form a superset. For instance, said large actuating set can comprise the electric actuators configured to actuate said blade, said swing member, said drive member, possibly including said right track drive device and said left track drive device.
In case the blade actuator is activated, then automatically the drive member (right and left track drive devices) are unlocked. However, in case one of right and left track drive devices is activated, the other one of left and right track drive devices can be activated, while the blade actuator remains unactivated.
According to an embodiment, the control method can further include a lock check step wherein said control unit checks whether said at least one electric actuator is currently locked,
wherein said control unit can perform said unlocking step in case said at least one electric actuator belonging to said at least one actuating set is currently locked.
In such an embodiment, both said actuation check step and said lock check step trigger the unlocking step. Said lock check step can occur before, after or during said actuation check step occurs. Thus, such a lock check step allows the control unit to release the static brakes only when they are currently locked. To check whether the or each electric actuator belonging to an actuating set are currently locked, the control unit checks whether the corresponding static brake is in its locking position or in its unlocking position.
According to an embodiment, said excavator can further include several position sensors, each position sensor being configured to detect the position of a respective electric actuator and to send position signals to said control unit, said control unit being further configured to determine the position of each one of said electric actuators based upon said position signals.
Throughout the present application, the term “position sensor” defines a device configured to electronically monitor the position or movement of a component, for instance of a movable member. A position sensor generally produces an electrical signal that varies as the position of said component varies.
Thus, such position sensors allow the control unit to monitor the positions of the electric actuators.
According to an embodiment, each position sensor can be an encoder coupled with an electric actuator.
According to an embodiment, said control unit can further comprise at least one timer for counting at least one predetermined period as from the start of said reception step, and wherein, after said predetermined period has elapsed without said control unit receiving any further command signal, said control unit can control said at least one static brake so as to move said at least one static brake towards its respective locking position.
Thus, in case the operator stops sending command signals to the control unit, such a timer permits to spare electric power, as it enables the control unit to lock again the static brakes instead of keeping energized the electric motors of the electric actuators belonging to the actuating set(s).
According to a variant, said excavator can comprise several actuating sets, and said control unit comprises at least one timer per actuating set.
According to an embodiment, said excavator can further comprise at least one temperature sensor configured to measure the temperature of said at least one electric actuator and connected to said control unit, said control method can further include a cooling step wherein, in case said
temperature exceeds a predetermined temperature threshold, said control unit can control said at least one static brake so as to move said at least one static brake towards its respective locking position.
According to a variant, said at least one actuating set can comprise at least one hydraulic actuator, said excavator can comprise at least one hydraulic static lock configured to lock said at least one hydraulic actuator, and said control unit can further be configured to control said at least one hydraulic actuator and said at least one hydraulic static lock.
According to a variant, said excavator can comprise at least one hydraulic actuation set comprising only hydraulic actuators and no electric actuator, said excavator further comprising hydraulic static lock configured to lock said hydraulic actuators.
Possibly, an operator may temporarily switch off or deactivate said control method, for instance via a button or a via human machine interface.
According to another aspect of the invention, an excavator includes at least:
several movable members, each movable member being configured to move at least a part of said excavator,
at least one actuating set comprising at least two actuators, said at least two actuators including at least one electric actuator configured to actuate at least one of said movable members,
at least one static brake movable between: i) a locking position where said at least one static brake locks said at least one electric actuator, and ii) an unlocking position where said at least one static brake unlocks said at least one electric actuator,
a command device configured to receive commands from an operator and to generate command signals based on said commands,
a control unit configured to receive said command signals and to control said actuators and said at least one static brake based on said command signals, said control unit being further configured to perform at least:
a reception step wherein said control unit receives a command signal,
an actuation check step wherein said control unit checks whether said command signal requires said control unit to actuate an actuator belonging to said at least one actuating set, and
in case said command signal requires said control unit to actuate an actuator belonging to said at least one actuating set, an unlocking step wherein said control unit controls said at least one static brake so that said at least one static brake moves towards its unlocking position.
Thus, such a control method allows the excavator to generate smooth motions with small or null backlash in case two or more movable members need be moved simultaneously or concomitantly.
According to a variant, the excavator further includes a switching device configured to switch the operation of said control unit between a inactive mode where said control unit temporarily operates without performing said reception step, said actuation step and said unlocking step, and an active mode where said control unit performs said reception step, said actuation step and said unlocking step.
Thus, an operator may temporarily switch off or deactivate said control method, for instance via a button or a via human machine interface.
Within the scope of the present invention, the afore-mentioned embodiments and variants can be considered either in isolation or in any technically possible combination.